1. Field
The disclosed embodiments relate to a device for separating a partial quantity of threads from a layer of threads with a movable separating means, a method for operating the device and a use of the device.
2. Brief Description of Related Developments
In many industrial processes based on the processing of threads (e.g. method for producing fabrics, textiles, etc.), the handling of thread layers consisting of a plurality of adjacently arranged, for example, parallel, threads plays a central role.
For example, the warp threads of a warp such as are processed on weaving machines are generally arranged more or less closely adjacent to one another and thus form a mostly flat (warp) thread layer. In this case, more or less large gaps are usually formed between neighbouring threads of the thread layer, the size of these gaps being related on the one hand to the yarn count (diameter) of the threads used, their condition such as hairiness, for example, and on the other hand, to the degree of fineness, the weight or the density which the fabric to be produced from the thread layer should have.
An elementary process step for handling a thread layer is the separation of threads from the thread layer. In this process step, a single thread or a partial quantity having a predefined number of threads is grasped and parted or separated from the remaining threads of the thread layer to allow individual further treatment of the respectively separated threads (independently of the remaining threads in the thread layer). By repeatedly applying the process step, all the threads of the thread layer can be successively separated and each subjected to further individual treatment.
The aforesaid concepts for processes for separating threads from a thread layer have found a number of applications in industrial production.
A typical application relates, for example, to the preparation of a weaving machine for the production of fabrics, where usually a plurality of (warp) threads must be drawn individually through various openings provided in the loom harness (for example, the opening for the thread eyelet in a heald). For this purpose, in each case the thread instantaneously forming the edge on a predefined side of the thread layer is usually separated from a prepared thread layer and then threaded through an opening assigned to this thread in the loom harness and this process is repeated until all the threads of the thread layer have been processed.
Another typical application relates, for example, to tying machines which have the task of tying threads of a first thread layer to threads of a second thread layer (for example, by means of knotting) to join the first thread layer to the second thread layer. For this purpose, a tying machine usually separates respectively one thread at the edge of the first thread layer and one thread at the edge of the second thread layer, ties one end of the one separated thread to one end of the other separated thread and repeats this process until each thread of the first thread layer is joined to each thread of the second thread layer.
In devices for separating threads from a thread layer, an important requirement is that the number of threads separated in a single work step should be monitored exactly: should the number of threads separated in one work step differ from a predetermined desired number, uncontrolled irregularities can then occur in subsequent work steps which can lead to reduced quality of the products to be produced and possibly to unusable products.
EP0206196 discloses a device for separating a single thread from a thread layer by means of a movable separating means. The separating means of this device is configured as a so-called separation needle which comprises a needle tip and a notch disposed on a side flank of the needle tip. For separating a thread at the edge, the needle tip is brought in contact with the thread to be separated and moved in its longitudinal direction until the thread to be separated is gripped by the notch, in which case the separation needle in the area of the notch is at least partly inserted into a gap between the thread to be separated and an adjacent thread. During a further movement of the separation needle, the thread grasped by the notch is separated from the remaining threads of the thread layer. In order to ensure that the separation needle always grasps and separates precisely one thread, the shape of the notch must be adapted to the cross-sectional shape of the thread to be separated within narrow tolerances. Otherwise, there is a risk either that no thread will be grasped by the respective notch and separated or that a plurality of threads will be grasped and separated. Accordingly, the device must be fitted with various separation needles in order to be able to process threads of different thickness, which must optionally be exchanged when threads of different diameters are to be processed. Exchanging the separation needles is usually time-consuming. In addition, fitting the device with plurality of separation needles covering a particular range of yarn counts is costly. Another disadvantage can be seen in that even the manufacture of a single separation needle can be associated with high costs if the notch of the respective separation needle needs to be fabricated with high precision. The latter particularly applies to separation needles which are provided for separating relatively thin threads.